Yazar "Altin S." seçeneğine göre listele
Listeleniyor 1 - 7 / 7
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Effects of SnO on growth and physical properties of BSCCO whiskers(2012) Altin S.; Aksan M.A.; Balci Y.; Yakinci M.E.Superconductor whiskers doped with SnO have been fabricated by annealing a melt quenched (Bi2Sn1)-223 precursor using suitable heat treatment cycles. Approximately 5 ?m thick, 90 ?m wide and 5 mm long whiskers were fabricated, and their physical, electrical and magnetic properties were investigated. Crystallisation activation energies of glass phase fabricated were calculated to be 390 kJ mol-1 using Kissinger method based on the differential thermal analysis data. The Tc value of the whiskers was found to be 94 K from M-T measurement. The magnetisation of whiskers before superconducting transition increased with decreasing temperature, and after superconducting transition, the magnetisation of whiskers decreased, from positive to negative, due to the diamagnetic nature of superconductivity. The change on magnetisation dependence of applied magnetic fields (M-H) showed that whiskers have paramagnetic-diamagnetic multiphase structure. © 2010 Institute of Materials, Minerals and Mining.Öğe Electrical and optical properties of ZnO-Fe2O 3-SiO2 composite prepared by SOL-GEL method(2007) Canbay C.A.; Altin S.; Aydogdu A.; Aydogdu Y.; Yakinci E.The semiconductor composite was prepared from ZnO, Fe2O 3 and SiO2 transition metal oxides by sol-gel method. The surface morphology of the prepared samples were investigated by scanning electron microscopy (SEM). The activation energies of the samples in the extrinsic and intrinsic regions were found as 0.75 eV and 0.77 eV for ZFS-1 and 0.22 eV and 0.32eV for ZFS-2. The value of the optical band gap of the composite samples were calculated from the absorption coefficient depending on photon energy. The optical band gap of the samples were found as 1.60 eV and 1.70 eV for ZFS-1 and ZFS-2, respectively. © 2007 American Institute of Physics.Öğe Exploring the Impact of Lanthanum on Sodium Manganese Oxide Cathodes: Insight into Electrochemical Performance(John Wiley and Sons Inc, 2024) Whba R.; Altundag S.; Aydin M.G.; Kalyoncuoglu B.; Ozgul M.; Depci T.; Altin S.This investigation focuses on nominally La-doped Na0.67MnO2, exploring its structural, electrochemical, and battery characteristics for Na-ion batteries. X-ray diffraction analysis reveals formation of composite materials containing three distinct phases: P2-Na0.67MnO2, NaMn8O16, and LaMnO3. The bond structures of the powders undergo scrutiny through Fourier-transform infrared and Raman analyses, revealing dependencies on the NaO, MnO, and LaO structures. X-ray photoelectron spectroscopy and energy-dispersive X-ray dot mapping analyses show that the La ions are unevenly dispersed within the samples, exhibiting a valence state of 3+. Half-cell tests unveil similarities in redox peaks between the cyclic voltammetry analysis of La-doped samples and P2-type Na0.67MnO2, with a reduction in peak intensities as La content increases. Electrochemical impedance spectroscopy model analysis indicates direct influences of La content on the half-cell's resistive elements values. The synergistic effect of composite material with multiple phases yields promising battery performances for both half and full cells. The highest initial capacity value of 208.7 mAh g?1, with a 57% capacity fade, among others, is observed, and it diminishes with increasing La content. Full cells are constructed using an electrochemically presodiated hard carbon anode, yielding a promising capacity value of 184.5 mAh g?1 for sodium-ion battery studies. © 2024 Wiley-VCH GmbH.Öğe High Voltage Ga-Doped P2-Type Na2/3Ni0.2Mn0.8O2 Cathode for Sodium-Ion Batteries(John Wiley and Sons Inc, 2024) Liu H.; Hong N.; Bugday N.; Yasar S.; Altin S.; Deng W.; Deng W.Ni/Mn-based oxide cathode materials have drawn great attention due to their high discharge voltage and large capacity, but structural instability at high potential causes rapid capacity decay. How to moderate the capacity loss while maintaining the advantages of high discharge voltage remains challenging. Herein, the replacement of Mn ions by Ga ions is proposed in the P2-Na2/3Ni0.2Mn0.8O2 cathode for improving their cycling performances without sacrificing the high discharge voltage. With the introduction of Ga ions, the relative movement between the transition metal ions is restricted and more Na ions are retained in the lattice at high voltage, leading to an enhanced redox activity of Ni ions, validated by ex situ synchrotron X-ray absorption spectrum and X-ray photoelectron spectroscopy. Additionally, the P2-O2 phase transition is replaced by a P2-OP4 phase transition with a smaller volume change, reducing the lattice strain in the c-axis direction, as detected by operando/ex situ X-ray diffraction. Consequently, the Na2/3Ni0.21Mn0.74Ga0.05O2 electrode exhibits a high discharge voltage close to that of the undoped materials, while increasing voltage retention from 79% to 93% after 50 cycles. This work offers a new avenue for designing high-energy density Ni/Mn-based oxide cathodes for sodium-ion batteries. © 2023 Wiley-VCH GmbH.Öğe Intrinsic challenges and strategic approaches for enhancing the potential of natural rubber and its derivatives: A review(Elsevier B.V., 2024) Whba R.; Su'ait M.S.; Whba F.; Sahinbay S.; Altin S.; Ahmad A.Natural rubber (NR) and its derivatives play indispensable roles in various industries due to their unique properties and versatile applications. However, the widespread utilization of NR faces intrinsic challenges such as limited mechanical strength, poor resistance to heat and organic solvent, poor electrical conductivity, and low compatibility with other materials, prompting researchers to explore enhancing its performance. Modified NRs (MNRs) like cyclization, deproteinization, chlorination, epoxidation, or grafting NR demonstrated a few enhanced merits compared to NR. However, various strategies, such as blending, vulcanization, crosslinking, grafting, plasticization, reinforcement, and nanostructuring, overcame most drawbacks. This review comprehensively examines these challenges and delves into the modification strategies employed to enhance the properties and expand the applications of NR and its derivatives. Furthermore, the review explores future visions for the NR industry, emphasizing integrating advanced modification techniques, adopting sustainable practices, and promoting circular economy principles. By elucidating the inherent challenges, outlining effective modification strategies, and envisioning future trajectories, this review provides valuable insights for stakeholders seeking to navigate and contribute to the sustainable development of the NR sector. © 2024 Elsevier B.V.Öğe The mechanical properties of nanohybrid and bulk fill posterior composites(Scientific Publishers of India, 2018) Kamalak H.; Canan A.C.; Altin S.Objectives: The objective of this work was to investigate the structural properties, thermal conductivity, Differential Thermal Analysis (DTA), Thermo-Gravimetric analysis (TG), surface homogeneity, microhardness, X-ray analysis of nanohybrid and bulk fill composites. Methods: 108 rectangular specimens were prepared from the following composites: (Estelite Sigma Quick (ESQ), Charisma Smart (CS), 3M Espe Filtek Z 250 (EFZ) and Filtek Restorative (FR)) and subjected to various artificial aging protocols (storage in distilled water for 24 h; thermal cycling, 2 × 3000 cycles 5/55°C). The materials were light-cured for 20 s in a 2 mm × 2 mm × 6 mm teflon mould. The nanoparticles of groups were identified by FT-IR spectroscopy. Surface roughness measurements were carried out by optical microscope, the Vickers hardness number was measured with the stainless steel sheet using a micro-indentation tester (Emco Test Durascan), the heat conductivity of the samples was analyzed by the home made thermal conductivity measurement system, thermogravimetric analysis (DTG, 60-AH, Schimadzu) was used to determine the filler mass fraction. Thermogravimetric analysis was performed in argon atmosphere from 30 to 850°C. Results: It was found that the composites have multiphase component such as metallic dopant and organic binder. Conclusions: The XRD investigation showed that there was a broad halo in the pattern which indicates the organic section in the composites. We found that the temperature dependence of the thermal conductivity of the composites depended on the type of the composites, which are low enough for dental applications. The micro-hardness of the samples was analyzed and the result was compared with literature and it was found that the observed results were in agreement with literature. © 2018, Scientific Publishers of India. All rights reserved.Öğe Microstructural and dielectric properties of naphthalene based polyamide/?-Ni(OH)2 nanocomposites(Bentham Science Publishers B.V., 2018) Sezer S.; Öz E.; Altin S.; Vural S.; Gültek A.; Köytepe S.; Nilüfer Kıvılcım F.Background: Aromatic polyamides are important materials having outstanding thermal, electronic and mechanical properties among high performance polymers and industrial plastics. In addition, aromatic polyamides can be utilized in electronic devices with their low dielectric constant which indicates the storage capacity of these devices. Objective: Free volume is very important for dielectric materials and increase in free volume of a polymer reduces its dielectric constant. The aims of the current study are to create free volume in the bulk polyamide structure and to reduce the dielectric constant by using ?-Ni(OH)2 particles. Method: The composites obtained from ?-Ni(OH)2 (flower-like nanoparticles) in a naphthalene-based polyamide matrix were prepared. Firstly, ?-Ni(OH)2 nanoparticles were synthesized by microwave-assisted solvothermal technique under various reaction conditions. Then, polyamide/?-Ni(OH)2 composites were prepared via direct dispersion methods at different reinforcement ratios. Results: ?-Ni(OH)2 (flower-like nanoparticles) and polyamide/?-Ni(OH)2 composites were prepared successfully. Our studies showed that the dispersion of ?-Ni(OH)2 nanoparticles in polyamide matrix is homogenous and prepared composites have good thermal and dielectric properties with promising results for electronic industry. Conclusion: Dielectric properties of the prepared composites decrease with increasing ?-Ni(OH)2 nanoparticle content and all composites show low dielectric constant when ?-Ni(OH)2 nanoparticle content is over 1 wt.% compared to the pure polyamide. © 2018 Bentham Science Publishers.
